Core A will provide adenovirus technology services to Projects 1 to 3. New recombinant Ad-5 (delE1, E3) adenoviruses will be constructed in bacteria. We will supply the projects with purified viruses for the proposed in vitro and in vivo work. Core A will also develop and test second-generation, conditionally replicating adenoviruses that are under radiation-inducible or tumor-specific control. Second generation viruses will be evaluated for efficacy in vitro and in human xenografts.